A switchable film may generally comprise two substrates, with a switchable material disposed therebetween. Depending on the nature of the switchable material, it may be advantageous to provide a seal around the perimeter of the switchable material to keep it separated from water, air, oxygen or other aspects of the external environment. This may be beneficial in preserving function, or preventing degradation or diminished performance.
The configuration of the seal, and the manner in which is it applied or assembled for the switchable film or switchable device may be governed, at least in part, by the nature of the switchable material and how it is applied. Some electrochromic devices (e.g. electrochromic mirrors) may have the substrates and seals assembled and cured, to first to provide a chamber. The chamber is subsequently filled by vacuum-pulling the switching material into the chamber. As the seal material is cured or solidified before exposure to the switching material, undesirable reactions of the switching material with a component of an uncured, or partially cured seal is avoided. For a switching material coated onto a moving web or film, that is to be cut to a desired shape, this method of pre-assembly of the chamber, although it may have a good seal, would not be appropriate, and other ways to avoid exposing a switching material to an uncured, or partially cured seal material may be sought.
A useful aspect in the mass production of device which comprise one or more seals or seal systems, is the ability to detect a failure of the seal during the production process. A breach of a seal in a device may result in a product with reduced durability or function, or a device that has, or will, fail. In some cases, the breach of a seal system may not be detected, or detectable, for some time after fabrication or after several hours, days, months or years of service. Sale or use of an article comprising the switchable film with a deficient seal may result in costly warranty and or safety issues. Thus, it may be beneficial to employ a seal or sealing system, in a switchable device that includes one or more detectors, or indicators built into the seal that would make the device identifiable, or attract the attention of an inspector or user in the event of a seal breach during production or storage, or in use.